The disclosure relates generally to ceramic substrates and particularly to substrates that modulate the flow of fluid being passed through them.
Modern emission control devices are very efficient at converting emissions to benign products at high temperatures. For example, three-way catalysts (TWC) have been utilized for the removal of carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx) from the exhaust of automobile engines for many years. However, when temperatures are below a certain level, such as during “cold start” of a motorized vehicle, such conversion is relatively poor due to reaction rate and mass transfer limitations. Following cold start, the catalyst temperature and conversion efficiency increases. For a given polluting species, the time from cold start to the time the catalytic device converts 50% of the species to benign products is often referred to as the “light-off time.” This light-off time can typically be tens of seconds, if not longer. Because of increasingly stringent emission control standards, there is an ever increasing need to reduce light-off time without substantially sacrificing the overall longer term performance of the emission control device.